The Third Generation Partnership Project (3GPP) has initiated the Long Term Evolution (LTE) program to bring new technology, new network architecture, new configurations and new applications and services to wireless networks in order to provide improved spectral efficiency and faster user experiences.
There are many man-made and natural emergencies that may cause considerable damage over a wide-spread area. Hurricanes, typhoons, tornados, floods, chemical spills and explosions, for example, may cause significant loss of life and property. While certain governments and commercial agencies currently provide warnings via siren, radio and/or television, a public warning system incorporated in a wireless transmit receive unit (WTRU) in an LTE network may increase the probability that a large number of people may be forewarned of these dangers.
FIG. 1 shows an LTE control-plane protocol stack 100 in accordance with the prior art. The protocol stack 100 may be located in a WTRU 102 and an eNode B (eNB) 120. The stack includes the radio resource control (RRC) 104, 124, the packet data control protocol (PDCP) 106, 126, the radio link control (RLC) 108, 128, the medium access control (MAC) 110, 130 and the physical layer (PHY) 112, 132. The non-access stratum (NAS) 114, 144 may also reside in the WTRU 102 and a mobility management entity (MME) 140.
FIG. 2 shows an LTE user-plane protocol stack 200 in accordance with the prior art. The user-plane protocol stack 200 may reside in a WTRU 202 and an eNB 222. The user-plane protocol stack 200 may include the PDCP 204, 224, the RLC 206, 226, the MAC 208, 218 and the physical layer 210, 230.
In an LTE communication system, a WTRU and eNB may share operating parameters in order to communicate properly. One way for the eNB to inform the WTRU about operating parameters is for the eNB to transmit system information to the WTRU. System information is public information about how a WTRU communicates with a cell, such as transmission bandwidth, channel configurations, cell loading and power control parameters, for example.
There may be a relatively large amount of system information transmitted by an eNB in a cell. Therefore, in order to organize the transmission of the system information, the information may be divided into a number of system information blocks (SIBs). The types of the system information carried in a particular SIB is constant, but the value of the information carried in each SIB is subject to change.
Some SIBs may have the same scheduling requirements, such as periodicity. There may be more than one system information (SI) message transmitted with the same periodicity. Each SIB may contain a set of related SI parameters. Several SIBs have been defined in the prior art, including, for example, a Master Information Block (MIB). The MIB may include a limited number of frequently transmitted parameters. Another defined SIB is SIB type-1. SIB type-1 may contain scheduling information and may include indicators as to when SI messages are transmitted. System information master (SI-M) and system information 1 (SI-1) are special versions of an SI message only carrying a single SIB, namely the MIB and SIB type 1, respectively. The SI-M message is carried on a Broadcast Channel (BCH) while all other SI messages are carried on a downlink shared channel (DL-SCH). The system information carried on BCH is contained in the MIB. All other system information is carried on a DL-SCH.
A paging message may be used to inform a WTRU in RRC_IDLE state about a change in system information. A WTRU in RRC_CONNECTED state may monitor a physical downlink control channel (PDCCH) on a periodic basis and at a time specifically defined for this purpose. If a WTRU detects the system information change RNTI (Radio Network Temporary Identifier) on the PDCCH, the WTRU may determine that a system information change will occur at a next modification period boundary.
The SI-1 message includes a value tag that may indicate if a change has occurred in the system information other than the SI-M and SI-1. A WTRU may use this value tag upon returning from out of coverage to verify if the previously acquired system information is still valid. A WTRU may consider system information to be valid for at most 6 hours from the moment it was received.
FIG. 3 shows a functional model for a WTRU 300 in accordance with the prior art. The interface between a WTRU 300 and a network is the radio interface. A WTRU 300 may be divided into a number of domains, the domains being separated by reference points. Some defined domains are the universal subscriber identity module (USIM) domain 302 and mobile equipment (ME) domain 304. The ME domain 304 may be further divided into several components showing the connectivity between multiple functional groups. These groups may be implemented in one or more hardware devices. An example of such connectivity is the terminal equipment (TE) 306 to mobile termination (MT) 308 interface.
FIG. 4 is a block diagram of physical components 400 mapped to the functional diagram 300 of FIG. 3. The universal integrated circuit card (UICC) 402 may be a physical implementation of the USIM 302 of FIG. 3. The remainder of the WTRU 404 may physically represent the MT 308 of FIG. 3, and a personal computer 406 may physical embody the TE 306 of FIG. 3.
“Attention” (AT) commands may be used for controlling MT functions and GSM/Universal Mobile Telecommunication System (UMTS) network services from a terminal equipment (TE) through a terminal adaptor (TA). The use of AT commands assumes an abstract architecture. FIG. 5 shows a block diagram of an abstract architecture 500 that may incorporate AT commands. The architecture 500 includes a TE 502, an MT 506 and a TA 504 used as an interface between the TE 502 and the MT 506. The TE 502 may be a computer, for example. The MT 506 may send MT status messages 508 to the TA 504 and receive MT control messages 510 from the TA 504. The TE 502 may send AT commands 512 to the TA 504 and receive responses 514 from the TA 504. As shown in FIG. 5, the TA 504, the MT 506 and the TE 502 are separate entities. However, the TA 504 may be integrated under the MT 506 while the TE 502 is implemented as a separate entity (configuration not shown). Also, the TA 504 may be integrated under the TE 502, with the MT 506 implemented as a separate entity (configuration not shown). Lastly, the TA 504 and the MT 506 may both be integrated under the TE 502 as a single entity (configuration not shown).